Process for making acetylene using a plasma arc furnace



June 14, 1966 J. w. coLToN PROCESS FOR MAKING ACETYLENE USING A PLASMAARC FURNACE Filed 001;. 24, 1962 Q ill,

INVENTOR JOHN WH/TE COLTON MM C United States Patent 3,256,358 PROCESSFOR MAKING ACETYLENE USING A PLASMA ARC FURNACE John White Colton,Pelham Manor, N.Y., assgnor to Halcon International, Inc., a corporationof Delaware Filed Oct. 24, 1962, Ser. No. 234,898 10 Claims. (Cl. 26o-679) `This invention relates to the plasma technique in high temperaturechemical reaction, more particularly to processes and apparatus forproducing acetylene a-nd thelike materials from a plasma gas whichcontains at least minor amounts of hydrocarbons which tend to formpulverulent carbon and form a deposit thereof on the anode which caneasily choke the anode passage, and especi-ally to such processeswherein the plasma gas is hydrogen containing to 10% of methane `andt-he anode is subjected to vibration at a frequency in the audible rangeand at an amplitude in the range of from 1 to 20% of the d-iameter ofthe anode passage, whereby deposit of carbon is removed or prevented.

Plasma technology has achieved a measure of commercialization, and insuch processes for preparing acetylene from methane, the plasma gas ishydrogen conta-minated with minor amounts of lower hydrocarbons, e.g.,from 5 to 10% of'methane. These hydrocarbons tend to crack and depositcarbon under the plasma arc environment. This deposit chokes the anodepassage and requires shut-down. The art is confronted by the problem ofproviding even more efficient plasma processes which avoid suchdrawbacks and permit continuous eilicient operation.

`The discoveries associated with the invention and relating to thesolution of the above problems, and the objects achieved in accordancewith the invention as set forth herein include the provision of: aprocess for conducting a high temperature reaction by means of a plasmawherein a gas containing carbonaceous material is subjected to anelectrical arc to form a plasma and simultaneously tends to depositpulverulent carbon which tends to block the arc outlet, including theimprovement which comprises subjecting the arc zone to vibration at afrequency Within the audible range and at an amplitude of l to 20% ofthe average diameter of the arc zonev outlet, whereby objectionabledeposition of carbon is avoided; such a process wherein the plasma gasis hydrogen con-taining from 5 to 10% of a lower hydrocarbon, such asmet-haue, ethane, or the like; such a process wherein the hydrocarbon isprincipally methane; such a process wherein the hydrogen contains aboutof methane; such a process wherein there is an about 80% conversion ofmethane to acetylene per pass; such a process using an energyconsumption of about 55,000 kilowatt per hour, a hydrogen feed rate ofabout 975 pound mols per hour and a methane feed range of about 1200mols per hour; such a process using a plurality of arc outlet zones eachof about 1.5 inches average diameter; such a process using a vibrationof an aptitude of about 0.15 inch and of a frequency in the range of 20to 1000 cycles per second; such a process wherein the frequency is about100 cycles per second; an apparatus adapted for carrying out hightemperature reactions using a plasma including arc means provided with acathode and an anode as well as a plasma gas inlet and a plasma outlet,said means being provided with vibrating means for subjecting at leastsaid anode to vibration in its axial direction in a frequency in theaudible range and of an amplitude of l t0 20% of the average diameter ofthe arc outlet, and a reaction chamber flexibly connected with theplasma outlet, said chamber being provided with reactant inlet means andreaction mixture outlet means; and other objects which 3,256,358PatentedA June 14, 1 966 ICC will be apparent as details or embodimeiitsof the invention are set forth hereinafter.

The accompanying drawing is a schematic vertical sectional diagram of apreferred embodiment of the invention.

EXAMPLE 1 Referring to the accompanying dra'wing, acetylene is producedby passing a plasma gas such as hydrogen containing methane into theplasma arc, and the plasma formed is mixed with reactant gas (methane),andl the high temperature reaction takes place directly after this vmixing. The mixture is then rapidly cooled by coolant (water) and theresulting mixture is passed to usual recovery means. The by-producthydrogen is used as plasma gas.

Operation with an energy consumption of 55,000 kilowatt per hour using ahydrogen feed of about 975 1b. mols per hour containing 10% (mol)methane and a methane react-an-t gas feed of 1200 lb. mols per hour,there is obtained about 80% 'of acetylene basedv on the methane reacted.'Ihere is a deposit of powdered carbon on the anode and :this tends toblock the anode passage way, necessitating shutdown after an about onehour period of operation.

By vibrating the arc assembly using 10 anode nozzles (each of 1.5 inchesdiameter) and subjecting each to an axial vibration inthe audible rangee.g. cycles/ second, at an amplitude of about 0.15 in. (10% of thediameter of the anode passage), similar yields are obtained, but thereis no objectionable deposit of carbon so that the process may beoperated over long periods without shutdown due to clogging.

As to the apparatus, in the arc section, 1 isa casing made of insulatingmaterial, as forA example synthetic resin, such as polyethylene, nylon,or the like. This casing surrounds a body 2 of electrically conductivemetal as, for example, copper, copper alloy, brass, aluminum, steel, orthe like. vBody 2 has a central female threaded bore into which theelectrode holder 3 of conductive metal is screwed. The electrode holder3 has `an endadju-sting cap 4 of suitable electrical insulatingmaterials as, for example, synthetic resin or like. The body 2 also hasthe annular groove 5 in communication with the bores or conduits 6 andthe threaded conection 7, into which the water-cooled current conductoror cable 8 is screwed. Screwed on to the conductive body 2 is the body 9of insulating material as, for example, synthetic resin, such aspolyethylene, nylon, or the like. The bodies 2 and 9 are sealed to eachother by means of the gasket seal 10'. The insulating body 9 has acentral bore 12 of larger diameter than the electrode holder 3, whichsurrounds the electrode holder and is flared outwardly at its upper endin flow communication with the bores 6. The electrode holder 3 has atits lower end a central bore or passage 13 in communication with thethin hollow tube 14. The bore 12 is also in communication with thepassage L13 by means of the side bore 15. The lower end of theinsulating body 9 is provided with the-bore 16 in communication with thebore 12, and with a tube or pipe 17 provided as an extension of the bore16.

The lower end of the insulating body 9 is also provided with the bore1-8 having the pipe 19 provided as an extension thereof. The bore 18leads to an annular reces-s 20 in the insulating body 9. The bore 13 inthe electrode holder 3 is widened at 22 around the tube 14 and providedwith a passage way 23-24 leading to the bore 18 and recess 20. Ametallic pipe 25, preferably of copper, copper alloy, steel, or thelike, is tted around the insulating body 9 in the form of a casing andsealed thereto by means of the O-ring seals 26. The casing 25 isprovided with the threaded nipple 27 for connection tol a water-cooledelectrical cable. The nipple 27 leads into the recess 20.

Screwed into the lower end of the electrode holder 3 is permanentelectrode 28 constructed, for example, of tungsten or thoriatedtungsten. The electrode 28 is hollow and its hollow interior is largerthan the tube 14, so that the tube 14 extends down into the interiorthereof, leaving annular space between the inner wall of the electrode28 and the outer surface of tube 14. A nozzle body 29, preferably of thesame metal as the casing 25, is secured to the casing by means of theflange 30. A disc 31, of a refractory material, such as aluminum oxide,is positioned between the nozzle body 29 and the insulating body 9. Thedisc 31 has openings for the pipes 17 and 19 and is provided with acentral bore. The nozzle body 29 has the nozzle 32 tted therein. Thisnozzle, 32, of platinum, silver or preferably of copper, is soldered influid-type contact with the nozzle body, leaving the annular space 33therebetween. The annular space 33 is connected on one side with thepipe 17 by means of the bore 34 and on the other side with the pipe 19by means of the bore 35. The nozzle body and the refractory disc 3.1dene the enclosed chamber 36, into which the electrode 28 extends.

The insulating body 9 is provided with the female threaded connection 37leading into the gas passage 38, which leads to annular gas distributinggrooves 39, which in turn leads into the annular gas outlet space 40surrounding the electrode 28.

In place of the annular gap4 formed by the gas distributing groovesleading into the space 40, a single enclosed groove may be provided intowhich the passage 38 leads. This groove may be connected to the space 40by a multiple number of annularly positioned holes. These holes shouldpreferably be positioned at an angle from the center of the 'axis of theelectrode 28 so as to provide a controlled amount of swirl to the gas.'I'he holes may thus be positioned at an angle of itl-30 from the axisof the nozzle 28. In all cases it is extremely important that an evengas distribution around the electrode be provided.

The end of the electrode 28 has a frusto-conical shape, i.e., a conicalshape, the tip of which is flattened and extends partially into thenozzle 32, which is cylindrical in shape.

In operation water-cooled electrical cables are connected at 7 and 27.These cables are of conventional construction and consist of a metallicelectrical conductor surrounded by an insulation covering provided withcooling water passages through which cooling water is forced. Thecooling water from the water-cooled electrical cables 8 flows into theannular groove 5, through bores 6 and through the annular passage formedby bore 12. From the annular passage formed by bore 12 a part of thecooling water flows through the bore 15, bore 13 and tube 14 to theinterior of the hollow electrode 28, cooling the same, and up throughannular space around tube 14, out through the passages 2i3-24 into thebore 18, to the annular recess 20 and out through the water cooledelectrical cable connected at 27 to a suitable drain, or forrecirculation. Another portion of the cooling water from the annularpassage formed by bore 12 ows through the bore 16, pipe 17, bore 34,around vthe annular space 33, cooling nozzle 32 through the bore 35,pipe 19, bore 18, to the annular recess 20 and out through thewater-cooled electrical cable with the other portion of the water.

A source of electrical current as, for example, from a conventionalwelding generator, is connected to the watercooled cable 8. This currentflows through the conductive body 2 to the electrode holder 3 and thenup to the electrode 28. The lead of opposite polarity or ground isconnected at 27 and is in electrical communication with the nozzle 32 bymeans of the nozzle body 29 and casing 25.

With cooling water flowing through the water-cooled leads and the`device in the manner previously described,

and with a suitable source of current connected at 7 and 27, an arc maybe struck between the nozzle 32 and electrode 28, either by screwing theelectrode body 3 by means of the insulating cap 4 downwardly toinitially ystrike the arc and by retracting the same by screwing in thereverse direction, 'or by providing an initial highfrequency source ofalternating `current connected at 7 and 27. After the arc is struck thesame may be suitably `adjusted by screwing the electrode holder 3.

Prior to striking the arc the hydrogen plasma forming fluid at asuitable pressure is passed in at 37, passes through the passages 38-39to the outlet 40 into the chamber 36. The plasma forming gas will fiowalong the electrode 28 over the frust0-c0nical tip lof the electrode andthrough the nozzle. The plasma forming gas will form a sheath around thearc between it and the inner surface of the nozzle 32, constricting thearc and forcing the same through the nozzle, as is indicated at 41. Theplasma forming gas will be converted in the nozzle to a free plasma andwill leave the nozzle and pass out of contact with the arc as a freeplasma stream, being projected from the nozzle. The plasma forming gasis passed into the chamber 36, preferably at a velocity and/ or pressuresuflicient so that the same will emerge from the nozzle 32 as a freeplasma stream having a velocity of at least 5, and preferably of atleast 50 feet per second, and most preferably of at least 500-1000 feetper second.

The axial vibrating means is made up of member 55 attached to the arcmeans via weld 55a. It is attached to drive shaft 57 Via pin 56. Thedrive shaft is supported in bearings 58 and 59. The drive shaft isconnected with link 61 via pin 60, and the link 61 is attached via pin63 -to an eccentric drive 62, which may be powered by any convenientmeans such as .an electric motor (not shown). The bearings may besupported in known manner. If desired, the are means may be supported byflexible means e.g. (wire and spring support from overhead), or in anyconvenient manner.

rl `he reactor means is made up of a casing 49, to which is attachedexpansion joint 46 by means of weld 48. The expansion joint is connectedvia link and bolt connection means 44 and 45 to plate member 42 which isfixedly attached to the arc by screw means 43. There is a clearancebetween casing 49 and the plate 42, to allow for vibration or relativemovement of the plate relative to the casing 49. The casing is providedwith a cooling channel through which water is passed in via connection51 and out via connection 52. It is also provided with reactant gas feedmeans 50 and quench water feed means 53 as well as reaction mixtureoutlet means 54 which leads to usual recovery means.A

In operating the vibrator, the eccentric drive is operated at a speed ofrotation to give the desired rate of vibration. Instead of an eccentricdrive, any other convenient vibration means may be used. Additionalvibrations may be supplied in directions other than axial, if desired.Also, any convenient arc means may be used. Generally, the advantages ofthe invention are particularly apparent when the plasma forming hydrogencontains 5 to 10% of methane; however, the invention is operative withhigher lor lower amounts. Generally, the vibration is at frequency inthe audible range, and may be from 20 to 1000 cycles per second. Fromthe economic viewpoint, the lowest frequency which permits extendedoperation is to be preferred. The amplitude of vibration is in the rangeof about l to 20% of the average diameter ofthe anode passage, whichpassage may be of `a diameter in the range of about 0.5 to 3.0 inches.

Any convenient power consumption may be used as well as any convenienthydrogen feed rate and methane feed rate, provided the conditionsselected give a reaction temperature or condition such that the desiredconversion of methane to acetylene is obtained.

It is indeed surprising that one may achieve long continued operation inaccordance with the invention, especially in view of the markedeconomies resulting therefrom since it substantially minimizes oreliminates the need for high purification of the by-prod-uct hydrogenseparated in the recovery system and recycled.

In view of theforegoing disclosures,A variations and modificationsthereof will be apparent to one skilled `in the art, .and it is intendedto include within rthe invention all such variations and modificationsexcept as do not come within the scope of the appended claims.

What is claimed is:

1. In a process `for preparing acetylene from a plasma containing lowerhydrocarbons which tend to deposit pulverulent carbon which tends toblock the yarc outlet, the improvement which comprises subjecting theentire `arc zone lto vibration as a unit in the direction of the axisoft-he arc at a frequency within the audible range and at an amplitudeof 1 t-o 20% of the average diameter of the arc zone outlet, wherebyobjectionable deposition `of carbon is avoided.

the hydrogen conof about 975 pound mols per hour and a methane yfeedIrange of about 1200 mols per hour.

7. A process of claim 6 using a plurality of 4ar-c outlet zones each ofabout 1.5 inches average diameter.

8. A process of claim 7 using a vibration of an amplitude of about 0.15-inch `and of a frequency in the range of 20 to 1000 cycles per second.

9. A process of claim 8 whe-rein the frequency is about cycles persecond.

10. An apparatus adapted `for carrying out high temperature reactionsusing a plasma including arc means provided with a cathode and an anode`as well as a plasma gas inlet and a plasma outlet, said means beingprovided with vibrating means for subjecting said cathode and anode tovibration as a unit in the direction of the axis of said cathode andanode at a frequency in t-he `audible range and at an amplitude of 1 to20% of the average diameter of the larc outlet, and a reaction chamberexibly connected with the plasma outlet, said chamber being providedwith reactant inlet means and reaction mixture outlet means.

References Cited by the Examiner UNITED STATES PATENTS 1,597,277 8/ 1926Jakowsky 204-173 3,051,639 8/1962 Anderson 260-679 FOREIGN PATENTS1,296,664 5/1962 France.

ALPHONSO D. SULLIVAN, Primary Examiner. D. S. ABRAMS, AssistantExaminer.

1. IN A PROCESS FOR PREPARING ACETYLENE FROM A PLASMA CONTAINING LOWERHYDROCARBONS WHICH TEND TO DEPOSIT PULVERLUENT CARBON WHICH TENDS TOBLOCK THE ARC OUTLET, THE IMPROVEMENT WHICH COMPRISES SUBJECTNG THEENTIRE ARC ZONE TO VIBRATION AS A UNIT IN THE DIRECTION OF THE AXIS OFTHE ARC AT A FREQUENCY WITHIN THE AUDIBLE RANGE AND AT AN AMPLITUDE OF 1TO 20% OF THE AVERAGE DIAMETER OF THE ARC ZONE OUTLET, WHEREB YOBJECTIONABLE DEPOSITION OF CARBON IS AVOIDED.
 10. AN APPARATUS ADAPTEDFOR CARRYING OUT HIGH TEMPERATURE REACTIONS USING A PLASMA INCLUDING ARCMEANS PROVIDED ITH A CATHODE AND AN ANODE AS WELL AS A PLASMA GAS INLETAND A PLASMA OUTLET, SAID MEANS BEING PROVIDED WITH VIBRATING MEANS FORSUBJECTING SAID CATHODE AND ANODE TO VIBRATION AS A UNIT IN THEDIRECTION OF THE AXIS OF SAID CATHODE AND ANODE AT A FREQUENCY IN THEAUDIBLE RANGE AND AT AN AMPLITUDE OF 1 TO 20% OF THE AVERAGE DIAMETER OFTHE ARC OUTLET, AND A REACTION CHAMBER FLEXIBLY CONNECTED WITH THEPLASMA OUTLET, SAID CHAMBER BEING PROVIDED WITH REACTANT INLET MEANS ANDREACTION MIXTURE OUTLET MEANS.